A cellular network can include one or more base stations that each provide wireless coverage for a particular geographic area referred to as a cell. As demand for data capacity increases in cellular networks, additional cells are established to add data capacity. These additional cells can be relatively small cells as compared to larger cells, such as macro cells. Additionally, a small cell (e.g., a base station) can be deployed in a variety of locations by an end user or operator with little to no radio frequency (RF) planning unlike a macro cell which is typically installed after substantial network planning with site-specific configuration settings.
A base station added to a network may have self-configuration capabilities that enable the base station to select a physical cell identifier (PCI) that identifies the base station within the network. The PCI may be derived from a primary synchronization signal (PSS) sequence index and a secondary synchronization signal (SSS) sequence index. The PCI should be selected to avoid PCI collisions which occur when two neighboring base stations with overlapping coverage areas share the same PCI. For example, when two base stations with overlapping coverage areas have the same PCI, a user equipment (UE) in the overlapping coverage areas may be unable to distinguish between signals received from the two base stations. The inability to distinguish between the signals received from the two base stations can cause the UE to experience loss of processing gain, synchronization issues, and high decoding errors.
Both base station and UE perform cell search operations (e.g., sniffing operations) to identify PCIs of one or more neighboring base stations (e.g., one or more neighboring cells). The UE may perform cell search operations to identify one or more neighboring base stations to communicate with, such as a base station with a strongest signal for the UE to perform a hand off operation. A base station, such as a new base station associated with a small cell, may identify one or more neighbors to select one or more configuration settings, such as a PCI. As compared to the cell search operations performed by the UE, the base station wants to search other base stations that may be far away and/or that are associated with a very weak signal received by the base station that performs the cell search operations. Base stations that are far away and/or that are associated with a weak receive signal may be difficult to detect because of interference (e.g., competing signals) from base stations that are closer and/or that are associated with stronger signals receive by the base station that performs the cell search operations.
Cell search operations are intended to identify cell IDs while having a miss detection rate (e.g., a rate of not detecting a PCI) that is low and a false alarm rate (e.g., a rate of detecting a PCI that is not actually broadcast) that is low. To identify PCI values, a combination of PSS detection operations and SSS operations may be used. The PSS detection operation identifies a PSS index and the SSS operation identifies a SSS index. Each of the PSS and SSS detections operations may include identifying a value in a corresponding signal (e.g., a PSS or a SSS) and comparing the value to respective PSS threshold or SSS threshold. The thresholds are often predetermined values. If a particular threshold is too high, a false alarm rate may be low but a miss detection rate may be high and PCIs may not be detected. If a particular threshold is too low, a miss detection rate may be low but a false alarm rate may be high. In techniques that use a predetermined threshold and that implement successive interference cancellation, a probability of a false alarm increases with each successive interference cancellation because, as identified signal components are identified and removed, the remaining signals (including noise signals) become more pronounced and are more likely as being identified as a PSS or a SSS. Additionally, techniques that implement successive interference cancellation can be time consuming and computational complex as a PSS index and a corresponding SSS index are detected and followed by performance of successive interference cancellation prior to performing a next detection operation.